This invention relates to recycling materials made up of organic compounds and metals such as stainless-steel. More particularly, this invention is directed to an apparatus and method for processing waste tires to recover primarily carbon and stainless-steel.
Used vehicle tires pose a significant environmental threat. Even with sufficient landfill space, whole tires are too flexible to be placed in landfills. Storing waste tires above surface is unacceptable because whole tires not only take up a great deal of space, but also create habitat for insect pests and rodents. Waste tires may be incinerated but the combustion process releases massive amounts of pollutants into the atmosphere unless expensive scrubbing systems are used to clean incinerator exhaust gases. Incineration also leaves ash which must be disposed of in some manner. Also, waste tires must be shredded or otherwise comminuted into small pieces in order to burn efficiently in an incinerator.
It is a broad object of the invention to provide an apparatus and method which overcome the above-described the problems and others associated with the disposal of waste tires. Another object of the invention is to provide a waste tire treatment apparatus and process which recovers useful materials from the tires.
The method of recovering material from waste tires according to the invention includes reacting substantially whole waste tires with a molten reactant metal. The waste tires react with the molten metal to produce primarily carbon gas and metal salts in molten or gaseous form. After a reaction period during which time the waste tires are in contact with the reactant metal, the method includes removing non-reacted solids from the reactant metal. These non-reacted solids comprise mainly stainless-steel which was included in the tires. Removing any stainless-steel remaining after the reaction period prevents the stainless-steel from dissolving into the reactant metal and corrupting the reactant metal bath.
Importantly, the tire treatment method according to the invention does not require shredding or otherwise comminuting tires into small pieces, and therefore eliminates the expense associated with this processing step. Also, the present waste tire treatment method releases only hydrogen gas and perhaps nitrogen gas to the atmosphere. Substantially all carbon from compounds which make up the tires is recovered as pure elemental carbon. Other elements included in compounds which make up the tires are recovered as metal salts. Stainless steel recovered in the process may be reused.
The apparatus for performing the tire treatment method according to the invention includes a reactor vessel which may be charged with a suitable reactant metal, preferably including mostly aluminum. A heater associated with the reactor vessel heats the reactant metal to a molten state and a circulating system preferably associated with the reactor vessel and heater circulates fresh reactant metal into the reactor vessel. The apparatus also includes a tire positioning arrangement and a gas recovery arrangement.
At least one and preferably several tire carriers are included in the tire positioning arrangement. Each tire carrier comprises a structure on which waste tires may be loaded and then lowered into the molten reactant metal in the reactor vessel. Each tire carrier preferably includes an open support structure which allows the molten reactant metal to flow through the structure and around the waste tires as the carrier structure and tires are lowered into the reactant metal.
A carrier lift structure is associated with each tire carrier for moving each tire carrier between a loading/collecting position away from the reactor vessel and a reaction position within the reactor vessel. The tire lift structure includes an arrangement for moving each tire carrier vertically so that each carrier may be lowered into the reactor vessel and lifted from the reactor vessel. The tire lift structure is also capable of moving each tire carrier laterally away from the reactor vessel to the loading/collecting position. A cooling system may be associated with the tire lift structure for cooling each carrier and any non-reacted solids remaining after removal from the molten reactant metal.
The tire positioning arrangement also includes a tire submerging system including a tire contactor member and a contactor actuator. As the waste tires are lowered into the reactant metal on a tire carrier, the tires may tend to float on the surface of the molten reactant metal rather than sink below the surface. The tire contactor member is in position to move downwardly over the waste tires, pushing the tires into the molten reactant metal and holding the tires beneath the surface of the reactant metal for the reaction period.
The gas recovery arrangement includes a gas recovery hood which is placed in an operating position over the waste tires and tire carrier before the tires are submerged into the molten reactant metal. In the operating position, the lower edge of the hood extends below the surface of the molten reactant metal to form a seal with the surface of the reactant metal around the area in which the tires are to be submerged. Once the gas recovery hood is in the operating position, and preferably purged of air with a suitable inert gas, the tire carrier and loaded waste tires are lowered into the reactant metal.
The gas recovery hood collects process gases released from the surface of the molten reactant metal. The process gases include primarily gaseous carbon and gaseous metal salts along with hydrogen and perhaps nitrogen. The collected process gases are passed through an aqueous scrubber to cool and remove the carbon and metal salts. A suitable liquid/solid separator separates the solidified carbon from the scrubber effluent and the remaining solution is then treated by a suitable process to remove the metal salts.
The waste tire treatment apparatus and method of the invention quickly recovers carbon and stainless steel from substantially whole used tire carcasses. Both the carbon and stainless steel may be reused in various products. Also, the apparatus and method produce substantially no harmful gaseous emissions.
These and other objects, advantages, and features of the invention will be apparent from the following description of the preferred embodiments, considered along with the accompanying drawings.